Presently, the crack evolution law in a fracturing process of unconventional reservoir rock media is a “black box” problem. Therefore, the existing laboratory researches on the fracturing process of fracturing media of various phase states mostly focus on qualitative analyses of distribution characteristics of a crack network formed after fracturing, and an evolution process of the stress field which plays a decisive role in the initiation and propagation of the fracturing crack network is difficult to be visually displayed and accurately described.
In the conventional technology, the numerical simulation method is also used to quantitatively analyze the distribution and evolution law of the stress field in the crack propagation process. However, it is worth noting that a series of issues such as geometric model, boundary conditions, mesh model, unit contact and separation, material parameters, constitutive relations, fracture and damage criteria are required to be simplified in the numerical simulation. The simplified process and issues such as computational scale and computational efficiency may all significantly affect the computational accuracy of the fracturing stress field. In particular, due to limitation of experimental methods and test conditions, most numerical simulation results lack experimental verification, thus the accuracy and reliability of the numerical analysis remains widely controversial, and the numerical analysis is difficult to be directly applied on an engineering site.
Therefore, an experimental device is urgently to be provided presently, to realize visualization and transparent display of the evolution law of global stress field during complex crack network initiation and propagation in the fracturing process.